Content inspection bypass via ignored ZIP64 offset
Published Oct 7, 2025 · Updated Oct 7, 2025
Archive parsing inconsistency in CPython zipfile allows remote attackers to hide malicious content in crafted ZIP archives. The _EndRecData64 function ignores the ZIP64 EOCD locator's reloff value and reads the record immediately before the locator, allowing two central directories to yield different contents. Exploitation requires user interaction and a workflow that processes the same archive with CPython and another ZIP implementation, enabling inspection or package-validation bypass.
Summary
What happened
Archive parsing inconsistency in CPython zipfile allows remote attackers to hide malicious content in crafted ZIP archives. The _EndRecData64 function ignores the ZIP64 EOCD locator's reloff value and reads the record immediately before the locator, allowing two central directories to yield different contents. Exploitation requires user interaction and a workflow that processes the same archive with CPython and another ZIP implementation, enabling inspection or package-validation bypass.
The record
- CVE
- CVE-2025-8291
- Published
- Oct 7, 2025
- Updated
- Oct 7, 2025
- Vendor
- Python Software Foundation
- Product
- CPython
- Classifications
- CWE-1285, T1195.001
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Oct 7, 2025CVE publishedPublication date reported by the CVE source.
- Oct 7, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <=3.14.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- ZIP64 locator offset proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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